Nutrient content of eight African leafy vegetables and their potential contribution to dietary reference intakes

Abstract

Nutrient content and potential contribution of one average portion towards nutritional requirements (Recommended Dietary Allowance; RDA) of eight African leafy vegetables (ALVs) was determined. Compared to dark-green leafy vegetables (DGLVs) as sub-group, calcium and magnesium content were similar or considerably higher, vitamin C content was considerably lower, while pigweed had higher potassium content and spider flower similar folate content. All ALVs, except Chinese cabbage, had higher iron content. Black nightshade, pigweed, cowpea and spider flower leaves had higher β-carotene content than DGLVs. For children, pigweed and cowpea leaves emerged as good sources of vitamin A (>75% RDA), followed by spider flower, black nightshade, tsamma melon, Jew's mallow and pumpkin leaves (50 -75% RDA). For iron, pumpkin leaves provided 50 -75% RDA. Black nightshade, tsamma melon, pigweed and cowpea leaves contributed 25 -50% RDA, with Jew's mallow, spider flower and Chinese cabbage providing < 25% RDA. The ALVs were not a good source of zinc. Most ALVs were nutritionally similar to DGLVs. For most nutrients Chinese cabbage had considerably lower values than the other ALVs. Most of the ALVs can considerably contribute to requirements of vitamin A and, to a lesser extent, iron, both critical nutrients for developing countries.

Status of Underutilised Crops in South Africa: Opportunities for Developing Research Capacity

“…The popularity of leafy vegetables, also referred to as African Leafy Vegetables (ALVs), was attributed to their short growing season, high nutrient content, low agronomic requirements, drought tolerance, unique and acquired taste and their abundance in the wild [39][40][41][42]. More than 45 NUS have been documented to be in use [1,15,39,43,44]. Notably, the diversity of NUS was higher within the semi-arid region (Table 1) where they are collected and/or produced, and traded within informal markets.…”

Issues and Prospects for the Sustainable Use and Conservation of Cultivated Vegetable Diversity for More Nutrition-Sensitive Agriculture

“…present distinct amino acid compositions and are rich in ascorbic acid that is fundamental for optimal absorption of iron [95]. In addition to the roots, neglected leafy vegetables and species used for stems, shoots, and flowers may also merit greater research attention as these plant parts can provide important macro and micro nutrients to diets [46][47][48][49]96,97] and they were found to have received lower research attention than the multiuse vegetables. Since more than half of cultivated vegetables (58%) are used primarily for their leaves, we note that this large and poorly studied group of species could indeed offer a great diversity of opportunities for supporting more nutrition-sensitive agriculture.…”

“…Several indigenous leafy vegetables of Africa present an optimal source of nutrients such as β-carotene, folate, iron, calcium, zinc, proteins and dietary fibre [46][47][48][49], while showing lower water use and higher water use efficiency compared to introduced vegetables such Swiss chard (Beta vulgaris subsp. Vulgaris L.) [50].…”

“…Traditional vegetables can also require relatively fewer labour and economic inputs compared to global vegetables, meaning they present lower risks of financial losses for small farmers [55]. Because of their nutritional values and local adaptation, there is a growing body of literature highlighting how greater production and consumption of traditional and indigenous vegetables can support nutrition security and incomes [46,[56][57][58][59]. However, more research is needed to clarify and leverage the roles and potentials of specific species, as the complex relationships between nutritional yields, water availability, and soil quality [60,61] remain underexplored for many species, as do their acceptability to consumers and capacities for integration in value chains.…”

Effect of African leafy vegetables on the micronutrient status of mildly deficient farm-school children in South Africa: a randomized controlled study

“…However, homogenization was not used in meal preparation in studies found in the literature observing an improvement in serum retinol and in our study (11,27,29) . Although we did not analyse the β-carotene levels in our vegetables due to technical reasons, van Jaarsveld et al (31) reported that amaranth, cowpea, spiderplant and pumpkin leaves are rich in β-carotene (ranging from 4·2 to 7·1 mg per 100 g edible fresh weight (31) ). SF, serum ferritin; sTfR, serum transferrin receptor; ZnPP, zinc protoporphyrin; CRP, C-reactive protein.…”